Two types of press-fit techniques for mounting electrically-conductive contact members such as pins into the preformed typically plated-through holes in a PCB are known. In the first type, a solid pin is used, which has no spring energy.
The solid pin is press-fitted into the non-elastically-deformable area of the plated-through hole, and thus requires soldering for long term reliability. In a typical use for this method, to ensure reasonable retention force of the press-fitted connection prior to soldering, the plated-through hole tolerance for the solid pin is kept at .+-.0.002 inches or less, which increases PCB manufacturing cost to stay within such a tight tolerance. Further disadvantages include possible hole deformation and damage of the hole under-plating and trace circuit connections, which are initially undetectable and therefore detracts from long-term reliability.
The second type uses what is known as a press-fit compliant pin, which provides limited elastic deformation of a compliant section in the pin structure and does not require soldering. While this contact member can be removed, it cannot be reused due to permanent deformation of the compliant section. In a typical use for this method, the plated-through hole tolerance for the compliant pin is kept at .+-.0.003 inches or less, which still requires relatively high PCB manufacturing cost especially in punched versus drilled PCB holes. The tolerance is also hole-size related, which means that the smaller the hole, the tighter the tolerances required and the higher the fabrication cost. Examples of compliant pin constructions can be found described in U.S. Pat. Nos. 4,186,982; 4,464,009; 4,586,778; 4,740,166; 4,793,817.
The most common manufacturing method for both these types of pins is to stamp the parts from an unplated metal strip in a progressive die, utilyzing a carrier strip (ultimately removed as waste) to carry the pins through the manufacturing equipment. The carrier strip is used at times for continuous reeling of the pins for strip line plating and subsequent automatic placement (insertion into a connection housing or directly into the PCB). The customer-user is responsible for accommodating and ultimately disposing of the removed carrier strip. In the progressive die stamping process, a punch-in die removes metal between adjacent contacts pinned leaving sharp corners and rough surfaces. These conditions are difficult to eliminate due to the tooling not having effective access to the pin sides. As a result, when producing a press-fit pin in a progressive die from a metal strip, the press-fit section frequently causes PCB hole damage. Also, when there is a space between adjacent pins, the number of pins that can be packaged on a reel is reduced. Still further, it is desirable at times to produce press-fit pins that are round rather than square. Progressive die stamping cannot produce round pins.